Re: startx hanging - startup problem located

["martouf ." <martouf5 at gmail dot com>]

On Fri, 29 Apr 2005, Alexander Gottwald wrote:
>> uhh, don't you mean System(), Popen() and Pclose() ?  
>
> No. I mean Fopen. This is the only place where /bin/cat is mentioned.

oh yes, ok, I see now.  thanks.

>> They're contained within an entire "#if !defined(WIN32)" stanza and I'm not
>> sure what that means with respect to Cygwin.
>
> WIN32 is only for mingw and native compiler like msvc.

ok.  first time looking through XWin source, so I am completely
unfamiliar with its cpp vars.

> I've compiled XWin with HAS_SAVED_IDS_AND_SETEUID in os/utils.c
> http://www.freedesktop.org/~ago/XWin.exe.bz2
>
> Feel free to try.

thanks!  I did try, and it behaved like this:

1.  with "-kb" (kb ext disabled) it starts up just fine.

2. without "-kb" it 'hangs' with sh consuming >90% CPU right after the
'Rules' line. Ending the sh process causes XWin to wake back up and
finish starting up then runs just fine.

An interesting code pattern I see (and am not sure if it's
significant) in os/utils.c:

[paraphrasing]
Popen() {
 .
 .
switch (pid = fork()) {
 .
 .	execl("/bin/sh", "sh", "-c", command, (char *)NULL);
	_exit(127);
 }

    /* Avoid EINTR during stdio calls */
    OsBlockSignals ();
 .
 .
}

Pclose(){
 .
 .
    do {
	pid = waitpid(cur->pid, &pstat, 0);
    } while (pid == -1 && errno == EINTR);
 .
 .
    /* allow EINTR again */
    OsReleaseSignals ();
 .
 .
}
// with SIGCHLD set to SIG_IGN/SIG_BLOCK, then waitpid() should never
be interrupted
// by a signal and will never exit with EINTR.  It may exit with ECHILD, though.
// Does Cygwin behave the same way?

[more paraphrasing -- this next bit is more interesting to me]
Fopen(){
 .
 .
#ifndef HAS_SAVED_IDS_AND_SETEUID
    switch (pid = fork()) {
 .
 .
	execl("/bin/cat", "cat", file, (char *)NULL);
	_exit(127);
    }

    /* Avoid EINTR during stdio calls */
    OsBlockSignals ();
 .
 .
#else
 .
 .
}

Fclose(){
#ifdef HAS_SAVED_IDS_AND_SETEUID
    return fclose(iop);
#else
    return Pclose(iop);
#endif
}

// any chance at all what I'm seeing has something to do with the
EINTR || ECHILD possibility above?